While the impact of flu varies, it places a substantial burden on the health of people in the United States each year.
CDC estimates that influenza has resulted in between 9.2 million and 35.6 million illnesses, between 140,000 and 710,000 hospitalizations and between 12,000 and 56,000 deaths annually since 2010. Credit CDC.
It's exactly 100 years since the Spanish flu infected 500 million and killed an estimated 100 million people around the world.
Fast forward to 2018 and experts are worried another monster pandemic is emerging called "The Australian Flu!"
And the caveat is, this season's flu vaccines are no match for this new virus.
There are four types of influenza viruses: A, B, C and D.
Human influenza A and B viruses cause seasonal epidemics of disease almost every winter in the West.
The emergence of a new and very different influenza A virus is infecting people and causing an influenza pandemic in the West.
A devastating A virus- H3N2, sometimes referred to as the Aussie flu is proving to be "a very different influenza" and is causing concern among experts with a new influenza pandemic on the horizon.
The name Aussie flu comes from the H3N2 strain which caused big problems for Australia during their winter in 2017, which was their worst flu season in 10 years.
Fast forward to the Northern Hemisphere in January 2018, the CDC (Center for Disease Control) has announced deadly flu virus H3N2 has been killing around 100 people per week in the US since mid-December.
According to the Independent, A report published by the CDC with the latest figures showed there were 759 flu deaths between 7 October and 23 December.
It also said since early December more than 100 people were dying every week from the flu and the death toll could increase as there has been a further rise in the number of hospital admissions.
The Daily Mail claims flu fatalities have soared by 77 percent in just a week in England, Government figures reveal as fears of the worst outbreak in 50 years loom large.
In the UK, 149 people have so far died and last week 4,500 people were hospitalised, according to Public Health England figures.
Some 120 flu deaths have been recorded in England, 21 in Scotland and eight in Northern Ireland. There is no precise data available for Wales.
Another strain of flu, Yamagata or Japanese flu, was reported to have infected people in Greater Manchester this week.
Japanese flu is a subtype of Influenza B, whereas Aussie flu is a type A.
It has similar symptoms to other sub-types of 'flu but it's generally milder than A strains, according to Dr Coyle
He added: “Yamagata also tends to affect mainly children and is much more contagious as a result because children spread viruses more easily than adults.